1. Field of the Invention
This invention relates to a pulley unit provided with a one-way clutch. This pulley unit can be installed on an auxiliary machine driven from a crankshaft of an engine of an automobile or the like through a belt. As an auxiliary machine, cited are a compressor for an air conditioner, a water pump, an alternator, a cooling fan and so on of an automobile or the like.
2. Description of the Related Art
Various auxiliary machines installed on an automobile engine are driven through abelt by a crankshaft of the engine. Especially in thecase of an alternator among the auxiliary machines, if it is connected in such a manner as to be rotated synchronously with the crankshaft of the engine, when the rotating speed of the crankshaft drops, the power generation capability is lowered.
The applicant of the present invention has considered that the above one-way clutch is built in an alternator, whereby when the rotating speed of a crankshaft drops, the rotation of a rotor of the alternator is continued by its inertia force to heighten the power generation efficiency.
In this case, the one-way clutch is interposed between a pulley of the alternator and the rotor, and according to a rotational difference between the pulley and the rotor, the one-way clutch is switched between the free state (power transmission state) and the lock state (power transmission interruption state) to transmit or cut off power between the pulley and the rotor.
In the described one-way clutch, originally, it is necessary to detent a cage to a member where a cam face is formed for conducting the lock operation and the free operation. As a detent measure for the cage, the applicant of the present invention has considered the construction shown in the specification attached to Japan Utility Model Application No. 5-5162. That is, recessed cam faces formed in several areas of the circumference of an outer ring are extended to one axial end, and projecting parts engaged with the recessed cam faces are provided in the several areas of the circumference of the outer peripheral surface at one axial end of the case, whereby the cage is detented to the outer ring by the circumferential engagement of the projecting parts with the recessed cam faces.
As the conventional one-way clutch is so constructed that the existing recessed cam faces formed on the outer ring are applied to detent the cage, the following disadvantages are caused.
In the first place, the sectional form of the existing recessed cam face does not have a fixed radius of curvature unlike a circular arc. It is considered to be wasteful in respect of cost to work the sectional form of the projecting part corresponding to the recessed cam face with high accuracy only for detent for the cage, so conventionally the projecting part is set to be simply fitted in the recessed cam face. In such a structure, during the lock and free operation of the one-way clutch, the case is liable to be shaken due to the reaction force of an elastic member for energizing a roller, so that the responsiveness at the time of lock and free operation becomes bad and what is worse, there is the possibility that the complete lock state can not be attained. In situations where with the rotating operation of the outer ring body and the inner ring body, vibration is continuously caused, it is pointed out that the cage is sometimes displaced in the axial direction so that the roller is liable to skew and the lock and free operation becomes unstable.